The present invention relates to a switch that includes an N-shaped spring connected to an end of a bimetal plate. An adjusting screw is engaged with one end of the N-shaped spring so as to adjust the position of the end of the spring.
A conventional switch is shown in FIGS. 1 and 2 and includes a base 6 having an open top to receive a button 7 therein. Three terminal plates 61, 62 and 63 extend through three slots defined through the bottom of the base 6. The terminal plate 62 has a first contact point 922 and a bimetal plate 92 is located above the terminal plate 62. A second contact point 921 is connected to a bottom of the bimetal plate 92. An N-shaped spring 91 has one end pivotally connected to a recess 920 in one end of the bimetal plate 92, and the other end of the spring 91 is pivotally received in a groove 60 in an inside of the base 6. A swing member 83 pivotally connected between two opposite insides of the base 6 and a cone-shaped protrusion extends from an inside of the groove of the swing member 83 so as to define two recesses 831 separated by the protrusion. A connection plate 93 is pivotally connected to an end of the swing member 83 and the bimetal plate 92. A pushing rod 81 has a top end connected to an underside of the button 7 and a lower end of the pushing rod 81 can be inserted in either of the two recesses 831 in the swing member 83. A spring 82 is mounted to the pushing rod 81 to allow the button 7 to return.
As shown in FIG. 3, when pushing the button 7, the pushing rod 81 pushes the swing member 83 counter clockwise so that the two contact points 921, 922 contact and the circuit is closed. The bimetal plate 92 is maintained its position after the N-shaped spring 91 is deformed below its critical deformation ling xe2x80x9cLxe2x80x9d, and the button 7 is biased upward by the spring 82. As shown in FIGS. 4 and 5, when pushing the button 7 again, the pushing rod 81 is pivoted the swing member 83 clockwise, and the two contact points 921, 922 are separated again to open the circuit.
When the current overrides, the bimetal plate 92 is supposed to be deformed and overcomes the force of the N-shaped spring 91 to separate the two contact points 921, 922. However, the spring force of the N-shaped spring 91 could be too large to be overcome by the deformation of the bimetal plate 92. The deformation efficiency of the bimetal plate 92 could not be large enough to provide enough deformation to the bimetal plate 92 such that the N-shaped spring 91 does not change its position and the circuit cannot be opened in time.
In accordance with one aspect of the present invention, there is provided a switch comprising a base having a button on a top thereof and three terminal plates respectively extend through the bottom of the base. A groove is defined in an inside of the base and an adjusting hole is defined in the base and communicates with the groove. A first contact point is connected to one of the terminal plates.
A bimetal plate is located in the base an N-shaped spring has one end thereof engaged with the groove in the inside of the base, and the other end of the N-shaped spring is pivotally connected to the bimetal plate.
A swing member is pivotally connected between two opposite insides of the base and a cone-shaped protrusion extends from a top of the swing member so as to define two notches separated by the protrusion. A connection plate is connected between an end of the swing member and the bimetal plate.
A pushing rod has a spring mounted thereto and is located between the button and the swing member. A lower end of the pushing rod is located in one of the two notches in the swing member.
An adjusting member is movably engaged with the adjusting hole and an end of the adjusting member contacts the N-shaped spring in the groove.
The primary object of the present invention is to provide a switch having an adjusting member which is movably engaged with the base of the switch so as to adjust the position of an N-shaped spring to ensure the deformation of the bimetal plate is able to overcome the spring force of the N-shaped spring when the current overrides.
The present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a preferred embodiment in accordance with the present invention.
FIG. 1 is an exploded view to show a conventional switch;
FIG. 2 is a cross sectional view to show the conventional switch is in open circuit status;
FIG. 3 is a cross sectional view to show the button of the conventional switch is pushed to close the circuit;
FIG. 4 is a cross sectional view to show the button of the conventional switch returns to its original position when the circuit is closed;
FIG. 5 is a cross sectional view to show the button of the conventional switch is pushed again to open the circuit;
FIG. 6 is an exploded view to show the switch of the present invention;
FIG. 7 is a cross sectional view to show the switch in open circuit status;
FIG. 8 shows that the bimetal plate is deformed when the current overrides and the two contact points are separated;
FIG. 9 is an exploded view to show another embodiment of the switch of the present invention;
FIG. 10 is a cross sectional view to show the switch of the embodiment as illustrated in FIG. 9 is in close circuit status, and
FIG. 11 shows that the bimetal plate of the switch of the embodiment as illustrated in FIG. 9 is deformed when the current overrides and the two contact points are separated.